This invention relates to electronic power supplies, including power supplies used in amplifiers for musical instruments and sound reproduction, and more particularly to the variable control of the static operating point and dynamic behavior of power supplies for electronic amplifiers.
Musical instrument amplifiers function to not only increase the power of an input signal presented to the amplifier in order to drive a speaker or other load but also to modify the signal through the introduction of distortion and compression. The usual method of introducing distortion and compression is to configure the amplifier to produce so much gain that one or more of the amplification stages within the amplifier are driven beyond the limits of linear operation. Simply making an amplifier with exceeding amounts of gain, however, ignores the intricate dynamics that occur when an amplifier is driven to and beyond the limit. In particular, the power supply's interaction with the amplifier's operation has a substantial impact on the sound coloration produced by the amplifier.
Audio amplifiers, for both musical instruments and sound reproduction, have power supplies that usually include a transformer having its primary winding connected to AC line voltage supplied by a power company. The transformer's secondary usually consists of three windings. The first winding is used to produce the high positive DC voltage, and it is normally considered the amplifier's main power supply. The second winding, which may either be a completely separate winding or a section of the first winding, is used to create a negative DC bias voltage for the power tubes in the amplifier. The third winding is used to supply power to the tube heaters. The present invention is concerned with the amplifier's main power supply which is referred to herein as the "power supply."